1. Field of the Invention
The present invention relates to a pupil detection technology.
2. Description of the Related Art
With the advance of an increase in precision and processing speed, and downsizing of cameras, visual line detection devices that detect a position on an observation surface such as a monitor screen that a subject is gazing at, from an image of a face captured by a camera have been proposed. Initially, many of technologies require fixation of the head of the subject, and attaching of a detection device to the head. Recently, to decrease a burden of the subject, non-contact type visual line detection devices without requiring attaching of a device to the head have been developed, and visual line detection devices with higher precision are demanded. The non-contact type visual line detection devices detect a visual line according to a positional relationship between a pupil and corneal reflection on an image of the camera. Therefore, it is important to accurately obtain pupil center coordinates and corneal reflection center coordinates on the image of the camera.
Japanese Laid-open Patent Publication No. 2012-024154 proposes a technology that can stably detect a pupil using information of a corneal reflection image in a positive manner even if a most part of the pupil is hidden by the corneal reflection.
A contour of the pupil is originally a circular shape, but there is a case where the pupil is blocked by the corneal reflection, and a part of the pupil is lacked. Even for such an image in which the part of the pupil is lacked, it is desirable to detect a pupil center in a high accurate manner.